Trucks and heavy equipment, as well as some smaller machines, require drive trains to transmit power from a drive or input member to a driven or output member. For example, power may be transmitted from a transmission to a drive shaft, then to a differential and finally to a wheel. A truck with a long wheel base may require plural interconnected drive shafts between the transmission and differential. Components of the drive train, including drive shaft(s), transmission and differential, are typically coupled to one another by a universal joint. A large vehicle may have a drive train with as many as five universal joints.
It is sometimes necessary to uncouple one or more of the drive train (or drive line) components. For example, when a tractor trailer is towed, it is highly desirable to disconnect the drive shaft from the differential to render the transmission inactive. Otherwise, the transmission, which is unlubricated, might be damaged. Further, it may be necessary to uncouple one or more universal joints to repair or replace the components of the drive train or other components of the vehicle/machine.
The universal joint typically includes a cross shaft, with four radially extending trunnions, to which respective end yokes of the drive and driven members are connected. Each end yoke has a pair of yoke arms, each of which is secured to one of the trunnions of the cross shaft by a press fit bearing. The yoke arm acts as a collar to seat the bearing. Each press fit bearing, which includes an oval flange portion, is secured in place by its interference or press fit between the trunnion and yoke arm and by threaded studs securing the flange portion against the yoke arm. The bearings mounting the drive and driven members to the trunnions permit such members to pivot about their respective trunnions as rotary power is transmitted from the driving member to the driven member via the cross shaft. Thus, the universal joint permits power to be transmitted to a remote location not necessarily aligned linearly with the original source of power.
Even with the studs removed, it is frequently difficult to remove the bearings from their respective yoke arms because of their "press fit", a condition exacerbated with field used bearings due to swelling, rust and various other infirmities which lock them even more firmly in place. Moreover, it is virtually impossible to get a pulling or prying tool between the bearing flange and yoke arm to pry the bearing out of the yoke arm without damaging the bearing, yoke arm or both.
Several attempts have been made to solve this problem. One common approach is to hit, for example, the drive shaft with a maul or hammer to shift the drive shaft relative to the cross shaft and hopefully dislodge one of the press fit bearings from its "locked" position on the trunnion. This approach often results in damage to the drive shaft and usually is not successful. In fact, this approach is only successful if the bearing's interference fit is already fairly loose because of vibration or wear and tear on the interference surfaces of the yoke arm and bearing.
Another approach is to rotate the cross shaft until the end yoke of, for example, the drive shaft is disposed upright and then apply an upward force to the underside of the driven shaft with a jack. In theory, the weight of the truck will resist the upward force of the jack and cause the uppermost bearing of the upright end yoke to be dislodged. However, the forces locking the bearing in place are sometimes so large that the jack actually lifts the truck off the ground without dislodging the bearing from its interference fit.
Various tools have been designed in response to this problem, but they too have certain disadvantages.
One such tool is disclosed in Jirele U.S. Pat. No. 4,019,233. This tool operates to remove the press fit bearing of, say, the drive shaft by pushing the drive shaft end yoke in one direction and pulling the driven shaft end yoke in the opposite direction. Preliminary thereto, however, the studs fastening each bearing to its respective yoke arm are removed. Then, a "connect block" is secured to the yoke arm of the bearing to be removed by a pair of elongate studs which pass through openings in the bearing's flange portion and enter threaded bores of the yoke arm. In effect, such elongate studs replace the two studs that are removed from such yoke arm. Similarly, special side plates are mounted to both yoke arms of the driven shaft end yoke to provide gripping bosses for "puller arms" of the tool.
The puller arms and connect block are connected to a common, threaded drive stud, rotation of which causes a leveraged force to be exerted on the puller arms and connect block, and hence driven shaft end yoke and drive shaft end yoke, urging them in opposite directions. This in turn forces the one drive shaft bearing out of its yoke arm. The procedure is then repeated for the other bearing of the drive shaft. Once both bearings of the drive shaft are removed, it is unnecessary to use the side plates to remove the bearings of the driven shaft because the puller arms can engage directly the freely accessible trunnions of the cross shaft.
This tool has a time-consuming set-up procedure which is undesirable. It is costly to manufacture and more susceptible to operating problems because of the number of parts required, which is undesirable. Also, it applies a substantial force at the stud-receiving threaded bores of the yoke arm which could damage the same. Moreover, the tool requires a different connect block and set of side plates for each different universal joint, or at least a connect block and set of side plates specially adapted for use with yoke arms having varying spacings between their threaded bores.
A somewhat similar tool is disclosed in Stebbins U.S. Pat. No. 3,076,259. This tool includes a main body with opposed outwardly extending pins, puller leg supported by each pin, drive stud threadably engaged by the main body, and yoke arm engaging cup connected to one end of the stud. Like the Jirele tool, when the stud is rotated, a pushing force is exerted (by the cup) on the yoke arm of, for example, the drive shaft while a pulling force is exerted (by the puller legs) on the yoke arms of the driven shaft.
This tool will not work with a press fit bearing having a flange portion which overlies the yoke arm, as earlier described, and hence has limited utility. Moreover, the puller legs of this tool must be reversed once the press fit bearings of one shaft have been dislodged to remove the bearings of the other shaft. This is a time-consuming step which makes the uncoupling procedure less efficient. Finally, this tool requires a different set of puller legs for each universal joint of different size.
Baker U.S. Pat. No. 2,992,478 discloses a push-pull tool for removing axles. This tool appears to be unsuited for uncoupling universal joints of any type.
Other push-pull tools of questionable relevance are disclosed in Magavero U.S. Pat. No. 4,123,838; Shultz U.S. Pat. No. 3,487,528; Fillion U.S. Pat. No. 3,579,796; and Faber U.S. Pat. No. 1,469,076. These patents disclose tools for pulling plumbing handles, pulling valve stems and compressing springs, and hence do not appear to be directed to a problem even analogous to that addressed by the present invention.
Accordingly, there is a need for an improved drive-line puller that is simple, effective, relatively inexpensive to manufacture, efficient and easy to set up.